The invention relates to a liquid crystal display device having a plurality of pixel electrodes arrayed in a matrix form and, in particular, to a liquid crystal display device in which wiring lines are formed along the rows and columns of the pixel electrodes.
Recently, liquid crystal display devices of a high aperture ratio are demanded to attain high brightness or low power consumption. The aperture ratio can be improved by reducing a distance between a signal line and a pixel electrode, a distance between a scanning line and the pixel electrode, and a length which a light shielding film of a counter substrate overlaps the pixel electrode, within a range admissible in the manufacturing process.
In ordinary TFT (Thin Film Transistor)-type liquid crystal display devices, liquid crystal molecules are reversely tilted up in the vicinity of the scanning and signal lines due to lateral electric fields present between the scanning line and the pixel electrode and between the signal line and the pixel electrode. Thus, as shown in FIG. 1, a disclination line appears in a boundary area between the liquid crystal molecules tilted up at one end and the liquid crystal molecules tilted up at the other end. In this boundary area, it is difficult that the liquid crystal molecules are controlled to have a tilt-up angle corresponding to a voltage applied to the pixel electrode. If such a disclination line is located within the aperture for each pixel, defects such as a poor contrast, irregular image and residual image occur in the display operation, thereby degrading the display quality. To solve the aforementioned problem, the light shielding film is formed in a size capable of masking the disclination line.
Further, a dual domain technique, for example, is utilized for reducing the dependence of the liquid crystal display device upon a viewing angle. In this technique, each pixel is divided into two domains and the liquid crystal molecules in one domain is aligned in an orientation opposite to that of the liquid crystal molecules in the other domain by means of an alignment film, so that the liquid crystal molecules to be tilted up under the applied voltage have pretilt-base ends reversed for each domain. Also in this case, a disclination line appears at the peripheries of the domains. Conventionally, a storage capacitance line is formed to have a shape capable of masking the disclination line so as to avoid the defects caused in the display operation by the disclination line.
In the structure as shown in FIG. 1, however, the disclination line is crooked in a pixel area near an intersection between the scanning line and the signal line. Since the disclination line is masked by increasing the overlap length which the light shielding film of the counter substrate overlaps the pixel electrode, the aperture ratio is lowered.
In the case where the dual domain technique is employed to reduce the dependence upon a viewing angle, the disclination line is also crooked near a boundary between the domains and not parallel to the scanning line, as shown in FIG. 2. Since the storage capacitance line must be formed such that the disclination line is masked, it is difficult to attain a sufficient aperture ratio.